1. Field of the Invention
The present invention relates to a battery charger for simultaneously charging multiple storage batteries, and more particularly to an apparatus and method for simultaneously charging the multiple storage batteries loaded in the multiple charging pockets of the apparatus by controlling the charging voltage and current according to the voltage types and current capacities of the batteries.
2. Description of the Related Art
The conventional battery charger for charging the storage batteries such as a Li-Ion battery used in a mobile phone must be provided with multiple DC power sources in order to simultaneously charge multiple batteries. Referring to FIG. 1, the conventional battery charger includes an input terminal 10 for connecting with a power source of AC 110V to 220V, and a full-wave rectifier 12 consisting of bridge diodes D91-D94 and a capacitor C2 for full-wave rectifying the AC power from the input terminal 10 to produce a smoothed DC voltage. A Zener diode ZD1, resistor R1 and diode D2 serve to block a higher voltage exceeding a prescribed voltage. The DC voltage from the full-wave rectifier 12 causes a primary coil L1 of a transformer 14 to induce a secondary voltage in secondary coils L2, L3 and L4. A power switch 16 is switched on/off to control the level of the secondary voltage induced in the secondary coils L2, L3 and L4 according to a switching control signal.
The secondary voltage induced in the secondary coil L2 is rectified by a first rectifying circuit 18 consisting of a resistor R3, diode D3 and capacitor C3 to stabilize the DC voltage supplied to the power switch 16. The secondary voltage induced in the secondary coil L3 is rectified by a second rectifying circuit 20 consisting of a diode D31 and capacitor C31. The rectified voltage from the second rectifying circuit 20 is smoothed by a smoothing circuit 24 consisting of a choke coil L31, capacitor C32 and resistor R31, charging the storage batteries. The secondary voltage induced in the secondary coil L4 is rectified by a third rectifying circuit 22 consisting of a diode D21 and capacitor C21, supplied to a chopper circuit 26, which consists of a first regulator U22, capacitor C22, coil L21 and diode D22, to adjust the rectified voltage of the third rectifying circuit 22 to a prescribed level.
A first charging voltage control circuit 40 consists of resistors R30, R71, capacitor C26, transistor Q24, and field effect transistor FET Q23 to supply or block the charging voltage to a first battery loaded in a pocket xe2x80x98Axe2x80x99 according to a charging on/off control signal generated by a microprocessor 46. A second charging voltage control circuit 42 consists of resistors R44, R72, capacitor C35, transistor Q34, and field effect transistor FET Q25 to supply or block the charging voltage to a second battery loaded in a pocket xe2x80x98Bxe2x80x99 according to a charging on/off control signal generated by the microprocessor 46.
A first charging voltage selection circuit 36 consists of resistors R27, R28, R29, variable resistor VR1, diode D23, capacitor C50, and transistor Q22, to set a first charging voltage fit for the voltage type of the battery loaded in the pocket xe2x80x98Axe2x80x99 according to a charging voltage selection control signal generated by the microprocessor 46. A second charging voltage selection circuit 38 consists of resistors R41, R42, R47, variable resistor VR2, diode D32, and transistor Q33, to set a second charging voltage fit for the voltage type of the battery loaded in the pocket xe2x80x98Bxe2x80x99 according to a charging voltage selection control signal generated by the microprocessor 46.
A first charging current control circuit 32 consists of resistors R34, R36, R37, R38, R88, R99, operational amplifier U23A, and transistors Q31, Q88, Q99, to regulate the DC current from the smoothing circuit 24, and to control the charging current according to first and second current control signals generated by the microprocessor 46 detecting the voltage type of the battery. The microprocessor 46 recognizes the voltage types of the first and second batteries loaded in the respective pockets xe2x80x98Axe2x80x99 and xe2x80x98Bxe2x80x99 by detecting the different resistance values of both batteries across resistors R62 and R63 respectively connected between the source voltage VCC and the C/F terminals of both batteries, to generate the first and second charging voltage selection control signals according to the voltage types of the batteries, and the switching control signals for supplying the charging voltages to the pockets xe2x80x98Axe2x80x99 and xe2x80x98Bxe2x80x99. It also generates first, second, third, and fourth current control signals according to the current capacities of the batteries, charging on/off control signal by detecting the value of the voltage corresponding to the current detected from the first charging current control circuit 32, and display control signal to indicate the charged state of the first and second batteries.
A charging current/voltage control circuit 34 consists of resistors R32, R40, R69, R70, operational amplifiers U24A, U24B, transistor Q37, capacitors C39, C44, C45, C46, C47, and photo-coupler PC1, to compare the charging voltage set by the second charging voltage selection circuit 38 with a prescribed reference voltage to generate a switching control signal for regulating the charging voltage corresponding to the voltage type of the battery, and a switching control signal for controlling the power switch 16 according to the charging current detected from the first charging current control circuit 32. A charging voltage control circuit 30 consists of a resistor R25, operational amplifier U26A, diode D24, and capacitor C24, to compare the charging voltage selected by the first charging voltage selection circuit 36 with a prescribed reference voltage so as to regulate the charging voltage supplied to the battery.
A second charging current control circuit 28 consists of resistors R20, R21, R22, R23, R24, R80, capacitor C23, operational amplifier U23B, and transistor Q21 to regulate the DC current from the chopper circuit 26, and to control the charging current according to the fourth current control signal generated by the microprocessor 46 detecting the current capacity of the battery.
First and second LED devices 48 and 50 each consist of a pair of green LED for signaling the battery fully charged and red LED for the battery not fully charged. In addition, simultaneously charging both batteries of the pockets xe2x80x98Axe2x80x99 and xe2x80x98Bxe2x80x99, both red and green LEDs are turned on to indicate that the second charging voltage is lower than the first charging voltage. A first regulator 44 adjusts the rectified voltage of the first rectifying circuit 22 to a predetermined level to generate a source voltage Vcc supplied to the charging apparatus.
Such a conventional battery charger requires multiple current sources, and thus, separate chopper circuits and voltage and current control circuits for controlling the current sources, so that its circuit is complicated to increase the size together with the cost.
It is an object of the present invention to provide a battery charger for simultaneously charging multiple storage batteries, which employs a single source voltage to alternately charge the multiple storage batteries at different time intervals alternately predetermined according to their current capacities, thus reducing the size and cost of the battery charger.
According to an aspect of the present invention, a battery charger for charging at least two storage batteries, comprises: a first charging pocket for receiving a first storage battery; a second charging pocket for receiving a second storage battery; a main controller for generating a power supply control signal, a charging voltage setting control signal according to the voltage types of the batteries inserted in the first and second charging pockets, and a charging current setting control signal according to the current capacities of the batteries; a voltage adjustment circuit for adjusting the charging voltage to the levels respectively fit for the voltage types of the batteries according to the charging voltage setting control signal; a current adjustment circuit for adjusting the charging current to the levels respectively fit for the current capacities of the batteries according to the charging current setting control signal; and a power supply control circuit for supplying or blocking the charging voltages to the batteries according to the power supply control signal.
The present invention will now be described more specifically with reference to the drawings attached only by way of example.